In general, a flexible hose is a hose that can be expanded and contracted within a predetermined range, and can be bent freely. Conventional flexible hoses have a plurality of pleats that project from an outer circumferential surface thereof so that the flexible hose can be expanded and contracted in a lengthwise direction thereof. Such hoses are often used in vacuum cleaners to connect a suction nozzle with a cleaner body.
FIG. 1 illustrates a partial sectional view of a prior art flexible hose 1. As seen in FIG. 1, the prior art flexible hose 1 has a plurality of pleats 13 formed on the outer circumferential surface of the hose body 11. Each of the pleats 13 is formed in a U shape. Both sides of the pleat 13 are formed to be substantially vertical with respect to the outer circumferential surface of the hose body 11. An inner space 13a of the pleat 13 is in fluid communication with the inside of the hose body 11. The plurality of pleats 13 allow the flexible hose 1 to be expanded and contracted within a predetermined range of sizes.
As illustrated in FIG. 1, when air flows inside of the flexible hose 1 (arrow A), some air enters the inner spaces 13a of the plurality of pleats 13 (arrow B). When air enters the inner spaces 13a of the plurality of pleats 13, noise is increased.
FIG. 2 illustrates a second prior art flexible hose 2. As seen in FIG. 2, the flexible hose 2 includes a hard steel wire 21 and a hose body 23. The hard steel wire 21 is formed in a helical shape, such as a coil spring, and the hose body 23 is formed of a composite resin film to cover the hard steel wire 21. Fold portions 25 are formed between pitches of the hard steel wire 21 on the hose body 23. The hard steel wire 21 and fold portions 25 allow the flexible hose 2 to be expanded and contracted in a lengthwise direction thereof.
When the flexible hose 2 is contracted, pleat spaces 27 are formed in a U shape between the fold portions 25 and the hard steel wire 21 positions in the pleat spaces 27. Therefore, when air flows inside the flexible hose 2, some air flows into the pleat spaces 27, which increases noise. Additionally, the flexible hose 2 of FIG. 2 creates another problem in that the hard steel wire 21 adds significant weight to the hose 2.